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// SPDX-License-Identifier: GPL-3.0-or-later
#include "ses.h"
// ----------------------------------------------------------------------------
// single exponential smoothing
struct grouping_ses {
calculated_number alpha;
calculated_number alpha_other;
calculated_number level;
size_t count;
};
static size_t max_window_size = 15;
void grouping_init_ses(void) {
long long ret = config_get_number(CONFIG_SECTION_WEB, "ses max window", (long long)max_window_size);
if(ret <= 1) {
config_set_number(CONFIG_SECTION_WEB, "ses max window", (long long)max_window_size);
}
else {
max_window_size = (size_t) ret;
}
}
static inline calculated_number window(RRDR *r, struct grouping_ses *g) {
(void)g;
calculated_number points;
if(r->group == 1) {
// provide a running DES
points = r->internal.points_wanted;
}
else {
// provide a SES with flush points
points = r->group;
}
return (points > max_window_size) ? max_window_size : points;
}
static inline void set_alpha(RRDR *r, struct grouping_ses *g) {
// https://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
// A commonly used value for alpha is 2 / (N + 1)
g->alpha = 2.0 / (window(r, g) + 1.0);
g->alpha_other = 1.0 - g->alpha;
}
void *grouping_create_ses(RRDR *r) {
struct grouping_ses *g = (struct grouping_ses *)callocz(1, sizeof(struct grouping_ses));
set_alpha(r, g);
g->level = 0.0;
return g;
}
// resets when switches dimensions
// so, clear everything to restart
void grouping_reset_ses(RRDR *r) {
struct grouping_ses *g = (struct grouping_ses *)r->internal.grouping_data;
g->level = 0.0;
g->count = 0;
}
void grouping_free_ses(RRDR *r) {
freez(r->internal.grouping_data);
r->internal.grouping_data = NULL;
}
void grouping_add_ses(RRDR *r, calculated_number value) {
struct grouping_ses *g = (struct grouping_ses *)r->internal.grouping_data;
if(isnormal(value)) {
if(unlikely(!g->count))
g->level = value;
g->level = g->alpha * value + g->alpha_other * g->level;
g->count++;
}
}
calculated_number grouping_flush_ses(RRDR *r, RRDR_VALUE_FLAGS *rrdr_value_options_ptr) {
struct grouping_ses *g = (struct grouping_ses *)r->internal.grouping_data;
if(unlikely(!g->count || !isnormal(g->level))) {
*rrdr_value_options_ptr |= RRDR_VALUE_EMPTY;
return 0.0;
}
return g->level;
}
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